1. Field of the Invention
The claimed invention relates to an optical device provided with a zooming mechanism.
2. Description of the Related Art
There is known an image pickup apparatus including an optical device, such as an image pickup lens barrel, provided with a zooming mechanism configured to change image pickup magnification by moving a plurality of optical lenses in an optical axis direction. As the zooming mechanism of the image pickup lens barrel, there is known, for example, a mechanism configured such that a lens holding frame holding a lens is engaged with a cam groove of a rotating cam cylinder, and such that the rotation of the lens holding frame is regulated by a rectilinear motion barrel, so as to move the lens holding frame in the optical axis direction.
In the image pickup lens barrel provided with the zooming mechanism, the size of the image pickup lens barrel itself tends to be reduced in accordance with the improvement of lens specifications. However, with the reduction of the size of the image pickup lens barrel, the stroke (extension amount) between extension and retraction times of a light amount adjusting member, which is required to be electrically connected by a flexible board inside and outside of the image pickup lens barrel, has been increased. For this reason, it has become difficult that a long flexible board corresponding to the stroke is accommodated in a U-shape conventionally used in general.
In order to accommodate the long flexible board in a space in the image pickup lens barrel at the time of retraction without increasing the size of the image pickup lens barrel, many studies have been made on a method for increasing the space itself in the image pickup lens barrel, and on a method for efficiently folding the long flexible board into the space. For example, at the time of the retraction of the image pickup lens barrel, the image pickup apparatus is in a non-image-pickup state. By using this, a technique has been proposed, in which a part of the flexible board is made to enter into the optically effective light path of the image pickup lens barrel at the time of the retraction of the image pickup lens barrel (see Japanese Laid-Open Patent Publication (Kokai) No. 9-211284). The technique is configured such that a space required only when the image pickup lens barrel is in an image pickup state is efficiently used at the time of the retraction of the image pickup lens barrel, and thereby the space for accommodating the flexible board is substantially expanded.
However, in the technique described in Japanese Laid-Open Patent Publication (Kokai) No. 9-211284, a flexible member, such as the flexible board, the accommodated state of which is unstable, is made to enter the optically effective light path of the image pickup lens barrel. For this reason, when the flexible board is made to enter the optically effective light path of the image pickup lens barrel, there is also a possibility that the flexible board is brought into contact with a lens, so as to damage the lens. Further, when the flexible board is made to enter the optically effective light path of the image pickup lens barrel, a time period during which the flexible board can be completely retracted from the optically effective light path needs to be added to a time period from when the power supply of the image pickup apparatus is turned on to when an object image formed on an image pickup element is outputted. This results in a problem that the start-up time of the image pickup apparatus is increased.